Reinforcing ultra-centrifuge rotors

ABSTRACT

The disclosure illustrates a method and apparatus for reinforcing ultra-centrifuge rotors to enable operation at significantly increased rates. The rotor is selectively reinforced around its periphery by a sleeve comprising a plurality of turns of a boron filament impregnated with a curable epoxy resin. The boron filament may be wound on a spindle to preform a sleeve which then is telescoped over the periphery of the rotor, or it may be wound directly on the rotor itself. An additional variation shows the boron filament wound on various spindles to preform a series of coaxial interfitting sleeves telescoped over the periphery of the rotor.

United States Patent 1191 Roy [ 1 Oct. 21, 1975 REINFORCINGULTRA-CENTRIFUGE ROTORS [75] Inventor: Paul A. Roy, Andover, Mass.

[73] Assignee: Avco Corporation, Cincinnati, Ohio [22] Filed: Sept. 2,1971 21 Appl. No.: 177,379

3,627,571 12/1971 Cass et al 264/D1G. 19 3,668,059 6/1972 Economy et al.57/140 R 3,702,054 11/1972 Araki et al. 57/140 R FOREIGN PATENTS ORAPPLICATIONS 365,963 1/1932 United Kingdom 57/76 Primary Examiner-GeorgeH. Krizmanich Attorney, Agent, or Firm-Charles M. Hogan, Esq.; AbrahamOgman, Esq.

[57] ABSTRACT The disclosure illustrates a method and apparatus forreinforcing ultra-centrifuge rotors to enable operation at significantlyincreased rates. The rotor is selectively reinforced around itsperiphery by a sleeve comprising a plurality of turns of a boronfilament impregnated with a curable epoxy resin. The boron filament maybe wound on a spindle to preform a sleeve which then is telescoped overthe periphery of the rotor, or it may be wound directly on the rotoritself. An additional variation shows the boron filament wound onvarious spindles to preform a series of coaxial interfitting sleevestelescoped over the periphery of the rotor.

6 Claims, 4 Drawing Figures [52] US. Cl.- 233/27; 57/76 [51] Int. ClB04b 7/06 [58] Field of Search 233/27, 1 R, 1 E, 26, 7; 57/76, 140 R;106/55; 117/46; 264/DIG. 19

[56] References Cited UNITED STATES PATENTS 618,196 l/1899 Ashworth etal. 233/27 1,827,648 10/1931 Greene 57/76 2,008,037 7/1935 Quantin 233/1R 2,372,983 4/1945 Richardson 57/76 X 2,436,726 2/1948 Moyer 57/762,525,469 lO/195O Anderson 57/76 2,965,220 12/1960 Naul 57/76 X3,429,722 2/1969 Economy et al.... 106/55 3,534,902 10/1970 Gilreath233/7 3,573,086 3/1971 Lambdin 117/46 REINFORCING ULTRA-CENTRIFUGEROTORS The present invention relates to ultra-centrifuges and moreparticularly to rotors incorporated in an ultracentrifuge assembly.

In recent years there has been a need by medical research for moreeffective centrification from batchtype centrifuges. This has been doneby increasing the R.P.M.s of the centrifuge rotors to as high as 48,000.

This is known as an ultra-centrifuge that subjects its contents to anextremely high centrifugal force field. However, this same force fieldcauses the stresses in the rotor to approach such enormous proportionsthat the material cannot resist the force produced by the centrifugalmultiplication of its own weight. Attempts have been made to form therotors from a low density, high strength material, such as titanium.However, this material has a strength to weight ratio that still limitsthe upper R.P.M.s that can be achieved.

Accordingly, it is an object of the present invention to substantiallyincrease the maximum capable operating R.P.M. of an ultra-centrifugerotor in a simplified and economical fashion.

This end is achieved by winding a plurality of turns of a low density,high strength, high modulus filamentary material so that it forms asleeve around the periphery of a rotor. The filamentary material then isimpregnated with a curable resin. The sleeve selectively reinforces theperiphery of the rotor.

In a more specific aspect of the invention the filamentary materialcomprises a boron filament.

The above and other related objects and features of the presentinvention will be apparent from a reading of the description of thedisclosure shown in the accompanying drawing and the novelty thereofpointed out in the appended claims.

In the drawing:

FIG. 1 illustrates a step in a method embodying the present inventionfor reinforcing the periphery of an ultra-centrifuge rotor;

FIG. 2 shows an ultra-centrifuge rotor whose periphery is reinforcedusing the method shown in FIG. 1;

FIG. 3 shows an enlarged view of an alternate embodiment of the presentinvention; and

FIG. 4 shows still another embodiment of the present invention.

Turning first to FIG. 2 there is shown an ultracentrifuge comprising arotor element 12 rotatably driven by a low torque, high R.P.M. motor 14.The rotor 12 as herein illustrated is for a batch-type centrifuge. Theliquid to be separated into its constituents is placed in a central bowl16 containing various baffles and bleed passages (not shown to simplifythe description of the invention). The rotor is rotated to separate theconstituents according to their specific gravity, as is the usualpractice for centrifuges. The rotor 12 has an annular peripheral wall 18which is positioned at a rather substantial distance from the axis ofrotation of the rotor. When the rotor is rotated at R.P.M.s approaching48,000, the internal hoop stresses limit the maximum R.P.M. that can beobtained. Therefore, in accordance with the present invention theperipheral wall 18 of the rotor 12 is selectively reinforced as follows:

A spindle 20 is mounted on a shaft 22 rotatably driven by a suitablemotor 24. A plurality of turns of a low density, high strength, highmodulus filamentary material 26 is wound around the periphery of spindle20 by the rotation of motor 24. The filamentary material 26 is wrappedin a predetermined pattern by feeding it through a guide 28 displaceablein a slot 30 in arm 32. An articulated link 34 extends from guide 28 toa crank arm 36 driven by motor 38. Motor 38 is snychronized with motor24 so that a predetermined pattern results from winding the filamentarymaterial 26 onto spindle 20. The filamentary material 26 passes aroundguide rollers 40 and through receptacle 42 containing a curable resinmaterial 44. Filamentary material 26 is fed from a supply reel 46 whichis appropriately braked to produce a given pretension in the filamentarymaterial 26 for relatively tight winding onto spindle 20.

Preferably the filamentary material 26 is comprised of a boron filamenthaving an average diameter of approximately 0.0056 inch. This boronfilament, for example, may be manufactured by vapor depositing a mixtureof boron trichloride and hydrogen onto thin tungsten substrates. Thistype of boron filament is available from the Avco Systems Division ofAvco Corporation, Lowell Industrial Park, Lowell, Mass. 01851. Thecurable resin material may be a mixture of 89% resin with l 1% hardenerby weight. The resin and hardener may be selected from a wide variety ofbrands well known to those skilled in the art. Brands that have givenacceptable results are: ERL-2256 Epoxy Resin, available from UnionCarbide, and Curing Agent Z, available from Shell.

The boron filamentary material 26 is wound onto spindle 20 and saturatedwith the resin material. It should be pointed out that the boronfilament 26 may be applied wet, as shown in FIG. 1, or applied dry andthen impregnated with the resin. The spindle 20 is wound with a largenumber of turns-to produce a number of layers of boron filament. It hasbeen found that 48 layers, for example, produce a sleeve 48 with apredetermined thickness (FIG. 2). After the boron filament is wound andthe resin cured, the sleeve 48 is slipped off of the spindle 20. Thesleeve 48 is then telescoped over the peripheral wall 18 of the rotor 12to selectively reinforce its periphery.

Preferably the diameter D of the spindle 20 is selected to be as near tothe outside diameter D of the rotor 12 as manufacturing tolerances willallow to produce an ultimate zero clearance fit between the sleeve 48and the peripheral wall 18 of rotor 12. It has been found thatmanufacturing variations in size can be compensated for by selecting thediameter D of spindle 20 to be approximately 0.003 under the diameter Dof rotor 12. This results in an interference fit between sleeve 48 andthe periphery of rotor 12. To telescope the sleeve 48 over the peripheryof rotor 12 the sleeve 48 is heated to expand it and the rotor 12 cooledto contract so that the two fit together. When they have reachedequilibrium temperatures the sleeve 48 is tightly held on the peripheryof rotor 12.

The sleeve 48 of the boron filament substantially reinforces theperiphery of the rotor 12 and enables a significant increase in themaximum R.P.M.s attainable. It has been found the the maximum R.P.M.scan be increased from 48,000 to 56,000 R.P.M. The reason for thesubstantial increase in performance is that the boron filament is anextremely low density, high strength, high modulus material. Typicalproperties of the boron filament are: a density of 0.094 lbs./in. amodulus of 58 X 10 PSI, and a tensile strength of 500,000 lbs. persquare inch. The modulus of elasticity of the boron is substantiallygreater than that for the titanium in the wall 18. Therefore the sleeveof boron fi'lament resists deformation due to the hoop stresses fargreater than the titanium in the peripheral wall 18 of the rotor 12thereby preventing deformation of the titanium.

Referring to FIG. 3 there is shown an alternate embodiment of thepresent invention. In this embodiment the peripheral wall 18 of therotor 12 is reinforced by three sleeves 50, 52 and 54. The totalthickness of these sleeves is the same as the thickness of the sleeve 48shown in FIG. 2. It has been found that the windings are compacted andquite uniform in their spacing in the initial turns making up the sleeve48. The turns thereafter tend to be less uniform and have a lower degreeof compaction. Therefore each sleeve 50, 52 and 54 is preformed from asmaller number of turns than that for sleeve 48 and then telescoped intoone another to form the resultant reinforcing sleeve for the peripheryof wall 18'.

The sleeves 50, 52 and 54, respectively, are formed by winding on threeseparate spindles using the procedure shown in FIG. 1 and describedabove. The diameter of the spindle for sleeve 50 is approximately theouter diameter of wall 18'. The diameters for the spindles used to formsleeves 52 and 54 are progressively larger. The boron filament is woundon the various spindles to a predetermined thickness so that the sleevesinterfit with one another with a zero clearance.

For manufacturing convenience the sleeves may be formed with aninterference fit relative to each other and to the wall 18 of rotor 12'.These are assembled by the heating and cooling method illustrated forthe method of FIGS. 1 and 2. For example, sleeve 50 is cooled, sleeve 52heated and telescoped over sleeve 50. Then both sleeves 50 and 52 arecooled. Sleeve 54 is heated and telescoped over sleeve 52. The coaxialinterfitting sleeves 50, 52 and 54 are heated and telescoped over rotor18' which has been cooled.

The methods described above are directed to an embodiment where theboron filament is wound on a spindle, cured, and then placed over therotor 12. In the embodiment shown in FIG. 4 the boron filament is wounddirectly on the periphery of wall 18" of rotor 12". The boron filamentwindings form a sleeve 56 which is received in an annular recess 58around the periphery of wall 18'. However, the sleeve may be wounddirectly on the smooth exterior surface of the rotor with generallyequal results.

Each of the methods described above enable a high degree ofreinforcement of the periphery of ultracentrifuge rotors which greatlyincreases the maximum operating R.P.M.s.

While a preferred embodiment of the filamentary material has been shown,it should be apparent to those skilled in the art that other materialswith similar properties may be used with equal results. For example,graphite in an epoxy matrix could be used.

Having thus described the invention, what is claimed as novel anddesired to be secured by Letters Patent of the United States is:

1. A reinforced ultra-centrifuge rotor comprising:

a. a titanium bowl element; and

b. a plurality of turns of a filamentary material having a lowerdensity, higher modulus of elasticity and higher tensile strength thantitanium, secured around the periphery of said rotor element, wherebythe maximum rate of rotation of said rotor is substantially increased.

2. A reinforced centrifuge rotor as in claim 1 wherein said filamentarymaterial comprises a boron filament.

3. A reinforced centrifuge rotor as in claim 1 wherein said filamentarymaterial comprises graphite in an epoxy matrix.

4. A reinforced centrifuge rotor as in claim 1 wherein said filamentarymaterial is preformed in the shape of a sleeve and telescoped over theperiphery of said annular rotor element.

5. A reinforced centrifuge rotor as in claim I wherein said filamentarymaterial is formed from a plurality of preformed sleeves of multi-layersof filamentary material, each being formed from a single run of materialand telescoped over one another and over the outer periphery of saidrotor element.

6. A reinforced centrifuge rotor as in claim 1 wherein:

said annular rotor element has an annular groove formed in the outerperiphery thereof;

said filamentary material is positioned around the periphery of saidrotor element in said annular groove.

Notice of Adverse Decision in Interference In Interference No'. 100,429,involving Patent No. 3,913,828, P. A. Roy, REIN- FORCINGULTRA-CENTRIFUGE ROTORS, final judgment adverse to the patentee wasrendered Mar. 10, 1983, as to claims 1, 2, 4, 5 and 6.

[Oflicial Gazette November 8, 1983.]

1. A REINFORCED ULTRA-CENTRIFUGE ROTOR COMPRISING: A. A TITANIUM BOWL ELEMENT, AND B. A PLURALITY OF TURNS OF A FILAMENTARY MATERIAL HAVING A LOWER DENSITY,HIGHER MODULUS OF ELASTICITY AND HIGHER TENSILE THAN TITANIUM, SECURED AROUND THE PERIPHERY OF SAID ROTOR ELEMENT WHEREBY THE MAXIMUM RATE OF ROTATION OF SAID ROTOR IS SUBSTANTIALLY INCREASED.
 2. A reinforced centrifuge rotor as in claim 1 wherein said filamentary material comprises a boron filament.
 3. A reinforced centrifuge rotor as in claim 1 wherein said filamentary material comprises graphite in an epoxy matrix.
 4. A reinforced centrifuge rotor as in claim 1 wherein said filamentary material is preformed in the shape of a sleeve and telescoped over the periphery of said annular rotor element.
 5. A reinforced centrifuge rotor as in claim 1 wherein said filamentary material is formed from a plurality of preformed sleeves of multi-layers of filamentary material, each being formed from a single run of material and telescoped over one another and over the outer periphery of said rotor element.
 6. A reinforced centrifuge rotor as in claim 1 wherein: said annular rotor element has an annular groove formed in the outer periphery thereof; said filamentary material is positioned around the periphery of said rotor element in said annular groove. 